American Amateur Baseball Congress [more]
Coordinates play among US leagues in seven age brackets, from sub-teens through adults. Includes rules, tournament dates, and list of regions and age divisions.
http://www.aabc.us/

National Adult Baseball Association [more]
NABA amateur baseball organization information, including tournament results, events and how to join.
http://www.dugout.org/

Over 50 Baseball [more]
Promoting an affordable week-long fantasy-camp type fun tournament in Las Vegas each October. Also promoting the establishment of local leagues nationwide.
http://www.dugout.org/dugout/tournaments/over_50/50home.htm

Roy Hobbs Adult Baseball [more]
Amateur baseball organization for adults over the age of 28.
http://royhobbs.com/

Vintage Base Ball Association [more]
Listing of rules, tournaments, members and contact information.
http://www.vbba.org